Dear Thomas,
> ...the difference might come from some details in the implementation of +U or > from some things related to the pseudo Indeed, the difference in pseudos might have an impact. But also there are important differences in the DFT+U implementations: - in VASP the PAW Hubbard projectors are used - in QE the atomic or ortho-atomic Hubbard projectors are typically used (but you can also try the PAW projectors but this requires pseudos with AE wavefunctions, see PWCOND/examples/example03) HTH Iurii -- Dr. Iurii TIMROV Senior Research Scientist Theory and Simulation of Materials (THEOS) Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 ________________________________ From: Kazume NISHIDATE <[email protected]> Sent: Monday, November 28, 2022 12:21:47 AM To: Quantum ESPRESSO users Forum Cc: Vivekanand Shukla; Iurii TIMROV Subject: Re: [QE-users] Problem in vc-relax calculation with Hubbard U in magnetic system Dear Thomas Brumme, I'm not familiar with the +U method and this is a general view. - One possibility is the difference in the relaxation route achieving the most stable state. In some cases, the system may be trapped in quasi stable state. Suppose that you get structure A in QE and structure B in VASP, both starting from the original structure G, you can compare the relative energies by performing the static scf calculations for A, B, and G. If both of the codes return the same order of energies, such as E(A) < E(B) < E(G), you can safely identify the stable structure (in this case the structure A). Be careful about the k-points and cutoff energies. The number of PWs of A must be different from that of B and you must maintain the accuracy by increasing the k-points and the cutoff. - Are you using dense k-points mesh and high cutoff energies in the relaxation process too? - Of course the difference of the pseudo/PAW potentials may influence the results. This is the reason why the VASP has variety of pseudo/PAW potentials for some elements. Try the same calculations using different pseudo/PAW sets. - Try the VASP relaxations without +U option. Will it return the same structure with +U? > 2022/11/28 0:43、Thomas Brumme <[email protected]>のメール: > In VASP the relaxation is not restricted and since both codes use more or > less the same theory, the difference might come from some > details in the implementation of +U or from some things related to the > pseudo. Do you have any feeling/idea if changing to a different > pseudo or something different concerning +U might influence the relaxation? > > Kind regards > > Thomas 西館数芽 Kazume NISHIDATE Ph.D Department of Systems Innovation Engineering, Graduate School of Science and Engineering, Iwate University 4-3-5 Ueda, Morioka, Iwate, 020-8551 JAPAN Phone:+81-19-621-6391 [email protected], [email protected] https://sites.google.com/site/nisidatelab/
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